Batts and rolls are available in widths suited to standard spacing of wall
studs, and attic or floor joists. Continuous rolls can be hand-cut and trimmed
to fit. They are available with or without facings.
Manufacturers often attach a facing (such as kraft paper, foil-kraft paper,
or vinyl) to act as a vapor retarderer
and/or air barrier. Batts with a
special flame-resistant facing are available in various widths for basement
walls where the insulation will be left exposed. A facing also helps facilitate
fastening during installation. However, it's recommended that you use unfaced
batts if you're reinsulating over existing insulation.

Blankets come in rolls of up to 64 ft. Batts are simply blankets pre-cut
into 4 ft. or 8 ft. lengths. Widths are standard 16 in. or 24 in. making
these forms of insulation best for wood framing that uses the same dimensions
between studs. Thicknesses include 3 in., 6 in., and 9 in., but a 1 in.
version is available for special applications like around sills and narrow
spaces inside masonry walls. The R-value for each of these thicknesses varies
with the material. Standard fiberglass blankets and batts have a thermal
resistance or R-values between R-2.9
and R-3.8 per inch of thickness. High-performance (medium-density and high-density)
fiberglass blankets and batts have R-values between R-3.7 and R-4.3 per
inch of thickness. See the table below for an overview of these characteristics.

Fiberglass batt insulation characteristics

Thickness (inches)

R-value

Cost (cents/sq. ft.)

3 1/2

11

12-16

3 5/8

13

15-20

3 1/2 (high density)

15

34-40

6 to 6 1/4

19

27-34

5 1/4 (high density)

21

33-39

8 to 8 1/2

25

37-45

8 (high density)

30

45-49

9 1/2 (standard)

30

39-43

12

38

55-60

*This table is for comparison only. Determine
actual thickness, R-value, and cost from manufacturer and/or local building
supplier.

Installation

The maximum thermal performance or R-value of blanket and batt insulation
depends heavily on proper installation. Therefore, it's best to have a certified
insulation installer do it. If you'd like to have it done professionally,
you should do the following:

Obtain written cost estimates from several contractors for the R-value
you need. Don't be surprised to find quoted prices for a given R-value
installation to vary by more than a factor of two.

Ask contractors about their air-sealing services and costs as well,
if needed.

To evaluate batt installation, you can measure batt thickness and check
for gaps between batts.

If you want to install the insulation yourself, carefully follow instructions
and the necessary safety precautions. The insulation's manufacturer may
offer instructions. You should also check your local building and fire codes.

Cost

Blanket (batt or roll) insulation and installation usually costs less than
other types of insulation.